Internal combustion engines of the two-stroke and four-stroke varieties are driven by the combustion of fuel in one or more combustion chambers. The combustion of fuel drives a piston to reciprocate within a cylinder. The piston drives a connecting rod, which drives a crankshaft to rotate. The rotation of the crankshaft is transferred to wherever power is required, such as the wheels of a vehicle.
The combustion of fuel within each combustion chamber can occur as frequently as several thousand times per minute, and each combustion event exerts a force on the piston. The force can cause deformation of the piston head, by causing a deflection of the portions of the piston that are laterally farther away from the piston pin and the pin bosses. The repeated deformation stresses the piston and may ultimately cause a fracture of the piston head and resulting damage to the engine.
One solution to this problem is to construct a piston with a piston head having increased thickness in order to better withstand the stresses. However, the attendant increase in the weight of the piston results in reduced engine efficiency as more force is required to cause the piston to reciprocate within the cylinder, particularly to cause the piston to quickly reverse direction up to several thousand times per minute as the piston reciprocates within the cylinder. The additional weight may also affect the performance of a vehicle powered by the engine, particularly in recreational vehicles where the weight of the engine can be a significant proportion of the weight of the vehicle.
Another solution to this problem, particularly in high performance applications, is to use forged pistons instead of cast pistons. While forged pistons are generally more durable than cast pistons, they are made of a denser material and are more expensive to mass-produce, adding cost to the engine.
Therefore, there is a need for a piston that can withstand the forces described above while limiting the weight of the piston.
There is also a need for a piston having sufficient strength that it is suitable for use in high-performance engines.